1. Field of the Invention
The present invention relates to an automated analyzer which automatically analyzes components of biological samples such as blood, urine, etc. More particularly, the present invention relates to an automated analyzer which collects a liquid from a sample vessel and a reagent vessel and discharges it into a reaction vessel.
2. Description of the Related Art
With automated analyzers, methods for discharging a sample into a reaction vessel are roughly classified into the following two types. A first method is a technique in which the leading end of a sample probe is brought into contact with the bottom of an empty reaction vessel and then the sample is discharged. A second method is a technique in which a reagent is pipetted first, the leading end of the sample probe is brought into contact with the reagent, and the sample is discharged into the reagent. In recent years, the amount of reaction liquid as well as the amount of reagent used per analysis have been reduced in terms of reduction in running cost, and accordingly the amount of a sample to be pipetted has been reduced to a minute amount. Further, in order to improve the throughput, measures for increasing the analysis speed has been actively taken. In particular, an increase in pipetting speed is also a very important factor. However, these conventional methods have the following drawbacks.
With the first method, the leading end of the sample probe or the bottom of the reaction vessel is damaged, resulting in degradation of the pipetting accuracy in many cases. Recently, the leading end of the sample probe is made thin and sharp in order to maintain the pipetting accuracy with a minute amount of sample pipetted, that is, 1 microliter or less, which makes the bottom of the reaction vessel and the leading end of the sample probe susceptible to damage. With the second method, it is necessary to clean the inside and outside of the sample probe for each pipetting because the leading end of the sample probe comes in contact with the reagent. The second method has drawbacks that the necessity to perform cleaning process in each cycle (for each analysis item) may impair the improvement in throughput and that a large amount of cleaning water is required. With the first method, it is only necessary to clean the inside and outside of the sample probe only when the sample is changed. JP-A-5-164764 discloses a compromise method as an improved version of the two methods. This method first discharges the reagent into the reaction vessel, and performs very severe control so as to stop the sample probe at the moment when the drop of the discharged sample liquid at the leading end of the sample probe almost comes in contact with the reagent. JP-A-6-242126 discloses a pipetting method that takes damage to the probe into consideration.